1. Field of the Invention
This invention relates to the field of fabricating optical devices, and, more particularly, to the field of fabricating optical devices including a planar light guide defined by two or more polymers with different refractive indices.
2. Technical Background
Optical components may be used to transmit and process light signals in various fields of technology, such as telecommunications, data communications, avionic control systems, sensor networks, and automotive control systems.
Generally, such optical components are classed as either passive or active. Examples of passive optical components are those which provide polarization control, transmission, distribution, splitting, combining, multiplexing, and demultiplexing of the light signal. Active optical components include those requiring electrical connections to power and/or control circuitry, such as laser sources and photodiode detectors, and/or to process light signals using electro-optic effects, such as provided by certain non-linear optical materials. It is known to use inorganic materials, such as glass and other materials comprised of silica, to produce optical components. The methods of manufacture of such inorganic optical components are based primarily on lithographic technologies used in the mass production of semi-conductor wafers. However, the subsequent connecting of optical fibers to such components is complex, and requires the use of active alignment techniques which become increasingly more difficult as the complexity of the components increase. Thus, the manufacture of complex optical components from inorganic materials is relatively difficult and expensive.
Organic optical components comprising polymeric materials are known using direct and indirect lithographic processes. In indirect lithographic processes, a master pattern is formed from an organic or inorganic resist material. The master pattern is then replicated by electro-deposition to provide a series of molds which are then filled with a suitable polymeric material to produce the organic passive optical components.
Organic optical components usually comprise two or more polymers having different refractive indices. The polymer having the higher refractive index when surrounded by the other polymer can function as a waveguide for the transmission and/or processing of a light signal. The higher refractive index polymer is usually introduced into the other polymer as a resin which is then cured. A higher refractive index polymer must be introduced in a precise and controlled manner in order to reduce optical loss from the resulting waveguide. Known processes used in the preparation of such waveguides lead to the formation of a relatively thick and uneven residual layer of resin in the organic optical component which when cured results in a relatively thick layer of polymer of variable thickness. This gives rise to problems such as unexceptably high optical losses, non-uniform output, and inconsistent performance, thereby reducing the incentive to use such organic optical components.
A method of preparing an organic optical component having improved characteristics, and which is intended to facilitate mass production, involves forming a first layer of an optically transmissive first polymer, forming a retaining feature or groove pattern in the first layer, forming a line of contact between a flexible dispensing layer and the surface of the first layer and progressively contacting the surface with the flexible dispensing layer such that the line of contact advances across the surface. A sufficient amount of a curable second polymer is then applied to substantially fill the retaining feature along the line of contact and cured. Sufficient pressure is applied along the line of contact such that substantially all of the resin which is surplus to that required to fill the retaining feature at the line of contact passes with the advancing line of contact thereby filling the retaining feature with resin. The resin filling the retaining feature may be cured as it passes the line of contact. Although this method may provide some improvement in precise positioning and control over the thickness of the waveguide core material than other known processes for preparing optical devices from polymeric materials, there remains a need for improved processes which provide greater precision and control in positioning of polymeric waveguide core material in an optical device.